Defrosting apparatus for evaporators



Oct. 3, 1950 Filed Jply 5. 1947 R. w. KRITZER DEF'ROSTING APPARATUS FOR EVAPORATORS 2 Sheets-Sheet 1 0m 3, 1950 R, w, KRITZER 2,524,568

DEF'ROSTING APPARATUS FOR EVAPORATORS Filed y 1947 2 Sheetsq-Sheet 2 i l 72 Z! 70 I60 I JTZU Zf P I fizz/(MM;

29" 3% lagazifi,

Patented Oct. 3, 1950 nnmosmo APPARATUS FOR EvAPoaA'roRs Richard W. Krltzer, Chicago, Ill. Application July 5, 1947, Serial No. 759,150

' 12 Claims. 62-4) The invention relates to defrosting apparatus for low temperature refrigerating systems.

In unit coolers which include an evaporator of the evaporator, the accumulation of frost, on the evaporator decreases the cooling efficiency and it is desirable to periodically defrost the evaporator to maintain this efllciency. I

One object of the invention is to provide an apparatus which will quickly and periodically defrost the evaporator-by submerging it in' a body of water and then drain the water from the chamber in which the evaporator is disposed.

Another object of the invention is to provide improved defrostingapparatuswhich is eflicient and is automatically controlled.-

Another object of the invention is to provide:

defrosting apparatus for evaporators, which is and means for circulating air over the surfaces simple in constructionand efficient in operation.

Other objects of the invention will appear from the detailed description. I

The invention consists in theseveral novel features hereinafter set forth, and more particu: larly defined by claims at the conclusion hereof.

In the drawingsi Fig. l is a diagrammatic view of apparatus exemplifying the invention, including a unit cooler through which air is impelled, the housing of the unit being shown in' section. a

Fig. 2 is a view of a modified form of the invention.

Fig. 3 is a section of the valve mechanism for controlling the flow of water to the unit housing and the draining of water therefrom, in the modification shown in Fig. 2.

' invention is exemplified in connection with aunitcooler which comprises a housing Ill and afseriesoffin-type evaporator coils II, I! and i3, disposed in the housing In. This housing is adapted'toretain a column of water of sufficient l-eightto submergethe evaporators during defrosting'periods. Housing I0 is provided at one side with aninlet M for ambient air, at its opposite side with an outlet forcooled air. A rotary fan [6 driven by an electric motor I! is mounted in housing l0 adjacent the inlet opening M for circulating air through the housing in contact with the evaporators. The upper portion of the housing at one side thereof, is curved as at IQ, for deflecting air from the inlet It to the evaporating chamber-in the housing, and at its opposite side, with a curved .wall l8 for directing the cooled air to the outlet opening IS.

The evaporators ll, lland I3 are connected in series, for the successive flow of refrigerant therethrough. The apparatus for circulating refrigerant through the evaporators, comprises a com pressor 20, of any suitabl type, an electric motor 2| for driving said compressor, a high pressure refrigerant line 22 leading from the compressor. a fin-type of condenser 23, the coil of which is connected to line '22, a receiver 24 for the liquid refrigerant, and a pipe .25 leading from the receiver 24 to an expansion valve 26. The low pressure side of valve 26'is connected by a pipe 27 to the coil of evaporator II. The outlet of evaporator II and the inlet or evaporator 12 are communicatively connected at 28. The outlet side of the coil of evaporator l2 and the inlet side of the coil of evaporator l3 are communicativelyconnected at 29. A low pressure line 30 connects the outlet side of the coil of evaporator II and the intake side of the compressor 20'.

Air circulated through the housing III by fan lfi contacts the coils and fins of the evaporator and is cooled thereby before it is discharged through the outlet I5. The. evaporators are ar-' ranged. in angular relation to'each other, with evaporator l2 extending vertically and the evaporators II and I3 being upwardly inclined toward each other to a baflle 3 I, which extends across the housing Ill.

In the operation of the refrigerating system the refrigerant under high pressure from compressor 20, passes through the condenser- 23 to the receiver 24 and from the receiver to the expansion valve 26, which releases the refrigerant for expansion in the coils of evaporators II, I!

and I3, and cooling the air passing through hous ing It. The expandedfrefrigerant passes from the evaporators to the suction side of the compressor for compression and re-circulation.

Expansion valve 26 controls the flow of refrigerant to the evaporators and is of the type which includes a pressure-responsive diaphragm in casing 42 for controlling the valve. A bulb 40 is disposed in thermally responsive relation to a por-.

tion of the low pressure refrigerant line 30 in housing l0, contains an expansible gas, and is vcomr'nunicatively connected to the diaphragm casing 42 for controlling the operation of the I passing through the housing the operation of the compressor to maintain a pre-determined' temperature range, for example, 1? to 5 Fahrenheit in refrigeration for sub-freezing temperatures.' I v In refrigerating apparatus for reducing the temperature of air to below the freezing point of water, frost accumulates on the surfaces of the evaporators, which reduces the heat transfer efiiciency of the evaporators. For maintaining this efficiency, periodical removal of the frost is necessary. The present invention provides apparatus which quickly melts and causes the periodical removal of the frost by submergence of limited periods of the evaporators in a body of water delivered into the housing Hi. In the form of the invention shown in Fig. 1, the defrosting apparatus comprises: a reservoir 35 containing a volume of water substantially equal to the volumetric cubical area of the space in housing l which contains the evaporating coils; a centrifugal pump 36 which is driven by an electric motor 31 and has its intake connected to the bottom of reservoir 35; a pipe 38 communicatively connecting the discharge side of the centrifugal pump 36 and the bottom of the housing ID. The pump when driven, will draw the water from reservoir 35 and deliver it into the housing iii. The volume of water in reservoir 35 is sufficient to fill the housing i0 substantially to the top of the'evaporators ll, 12 and I3, so that the evaporators will be completely submerged with water for quickly melting the frost on the evaporators. The reservoir contains a measured quantity of water so the housing will not be overfilled. When the pump 36 is stopped, the water from gage contacts 49 for starting the pump-motor 31.

Th operation of the defrosting device will be as follows: During the normal operation of the refrigerating system, switch 46 will remain positioned to close the circuit for fan motor i1 and open the circuit for pump-motor 31. When 'the evaporators become covered with frost, the heat transfer from the evaporators will be reduced, the

' temperature of the air passing through the houshousing ill will drain therefrom by gravity,

through pipe 38 and thepump 36 to reservoir 35. The pump is of the type which is provided with vanes which permit the backflow of water when the pump is idle.

The circuit for the operation of pump motor 31 includes line conductors 41, 48, in one of which contacts 49 are included which are engageable by switch 46 to open and close the circuit for said motor. Switch 46 is normally separated from the contacts 49, so that the motor 31 will be operated only during defrosting periods. The electrical circuit for the operation of fan motor l1 includes conductors 50, which are connected to line conductors 41, 48, respectively, and

a pair of contacts 52 included in conductor 5|. The circuit for motor 11 is normally closed at contacts 52 by switch 46 and the switch is opened I to stop the fan motor during the defrosting per riods.

Bellows 45 are communicatively connected to the low pressure line 30 for controlling the operation of the defrosting apparatus. Switch 46 is engageable by said bellows to alternately open and close the circuits for the pump-motor 31 and the fan motor l1. Switch 46 normally engages contacts 52 for closing the electric circuit for fan motor 11 and is shiftable by a spring 56 and controlled by the bellows to engage contacts 49 for. closing the electric circuit for the pump- I motor 31. The bellows are loaded to control the shift of switch 46 from its normal position upon a pressure drop to a pre-determined degree in line 30; for example, if the pre-determined presure during the normal operation of the refrigerating system ranges-from zero to pounds for an output which produces a temperature of 1 to 5 degrees around the evaporators, the bellows permit switch 46 to remain engaged with contacts 52 during the normal operation of the system and upon a pressure drop below that range in line 30, will permit spring 56 to shift switch 46 to interrupt the circuit at contacts 52 for stopping the operation of fan motor l1 and to ening l0 will rise, so that thermostat 2| will keep the electric circuit for the compressor motor 31 closed, and the compressor in operation. The pressure in line will decrease and the compressor will suck gas from the line 30 and produce a pressure drop in said line to a point below the minimum of the pre-determined range for the normal operation of the refrigerating system, for example, below zero; This drop in pressure in line 30 will cause the contraction of bellows 45. Switch 46 will then be shifted by spring 56 to disengage contacts 52 and stop the fan motor l1 and to engage contacts and start the pumpmotor 31. Pump 36 will'then deliver water from reservoir into housing 10 until the evaporators become submerged in the water and melt the frost or ice on the refrigerator, the water being usually at a sufficiently high temperature for this purpose. Thepressure in the evaporators will then be increased, which will produce a rise in the pressure in the suction line 30 to or above the pre-determined range for the normal operation of the system, or the pre-determined pressure for contracting bellows 45. Bellows will then expand and spring 56 will operate switch lever 46 to engage contacts 52 to close the circuit for the fan motor l1 and disengage the switch from contact 49 to open the electric circuit for pump motor 31 and stop the pump 36. As soon as motor 31 and pump 36 are stopped, the water from housing II) will drain through pipe 38 and pump 36 into reservoir 35 until the housing is completely drained. The refrigerating system will then be normally operated to circulate refrigerant through the evaporators, and the fan [6 will be operated to circulate air in contact with the evaporators and through housing In for cooling the air to the desired degree until the evaporators again become frosted, when the defrosting apparatus will be again operated as before described. The air delivered by the fan into the casing, will exert pressure on the water in the housing, to expedite the draining of the water therefrom after each defrosting period.

In the modification illustrated in Fig. 2, the defrosting apparatus is operable by water under pressure from a usual water supply. In this construction, switch lever 46 controls a circuit consisting of conductors 41 and,48' to a solenoid magnet which is adapted to operate a duplex valve generally designated 6! to control the delivery of water into the housing In for submerging the evaporators and to drain the water therefrom after defrosting has been effected. A pipe 63 from an ordinary water supply which is usually under pressure, is communicatively connected to a chamber in the casing of valve 6 I. A normally closed valve member 65 controls the flow of water from pipe 63 to a pipe 66, which discharges water into the housing l0. A drain pipe 61 from provided for passing any. excess of water into the chamber 10, from which it is discharged into pipe 1|. Valve members 65 and-Glare fixedly secured to a common stem 14, which is adapted to be shifted by the solenoid magnet 60. A spring II normally-urges the stem II, to close valve member 65 and to'openvalve member 89 so that during the normal operation of the refrigerating systennthe drain linefrom housing it will be open and the supply of water from'pipe 63 will be cut off at valve member 65. In this modification, bellows 45 control the actuation of the duplex valve in the same manner as the pump-motor 31 is controlled in the construction shown in Fig. 1.

When bellows 45 are contracted, as hereinbefore described, which occurs when defrosting is desired, switch lever 46 will 'close the circuit for solenoid 60 and shift stem 14 and valve members 65 and iisdownwardly to close valve 69 against its seat, and to close drain pipe 6'! and simultaneously open valve-member 65 so that water will flow from pipe 63 past valve member 65 and through pipe 66 into the housing l0, until the evaporators are submerged. When the column of water in housing HI rises to the level of the upper end of overflow pipe 12, the excess will drain through said pipe into chamber I0 and to drainpipe II. This flow of water will continue until bellows 45 are expanded, as before described, when theeyaporators have been defrosted. The bellows will then open the circuit for solenoid 60 Solenoid so will then be de-en'ergized and spring 15 will shift valve member 65 to cut off the delivery of water from pipe 63 into the reservoir and simultaneously open the drain-pipe 61 to empty the housing l0. the'water flowing through pine 61, chamber 68, pastvalve member 69, through chamber [0, to the drain pipe II. This exemplifies a device for defrosting apparatus for'evap orator coils, by submerging them, inwater, and in which the housing is filled with water from an ordinary supply line and drained therefrom.

In the installation of the defrosting apparatus illustrated in Fig. l, the, housing III with the evaporators are placed in the cold storage room or com artment. 2. portion of which is diagrammatically indicated at a, and the reservoir 35 and pump 36; are disposed outside of said room or compartment where they are sub ect to ambient' or non-freezing temperature, so that the water used for defrosting will be drained to the outside of the compartment and will notfreeze between defrosting operations. In the installation of the apparatus illustrated in Fig; 2 the duplex valve 6i and magnet 60 are located outside of the low temperature compartment so that the water will be drained from housing It, and the water in said valve and, the water-line will not freeze.

While the apparatus includes means for stopping.the fan It during defrosting operations, it may be desirable in some instances, for simplicity in the control devices, to permit the fan to operate during such operations.

The invention exemplifies apparatus for periodically defrosting evaporators disposed in a cooler through which air is circulated, which will be automatically started to deliver a column of water into the housing to submerge the evaporators and to drain the water from the housing upon the completion of the defrosting period.

The invention is not to be understood as limited to the details described, since these may be modified within the scope of the appended .housing having frostaccumulating surfaces, and

means for circulating refrigerant through the evaporator, of a reservoir for a body of water, a

pump-for forcing'water from the reservoir into the housing for submerging the evaporator during a defrosting period, connected to drain water from the housing back to the-reservoir at the end of a defrosting period, and means controlled by, the pressure of the refrigerant from the evaporator for controlling the delivery of water by the pump from the reservoir to the tank for defrosting periods and draining the water from the housing back to the reservoir atthe end of said periods.

'2. The'combination with a housing adapted to retain a body of water, an evaporator in the a pump for forcing water from the reservoir into the housing for submerging the evaporator during a defrosting. period, connected to drain water from the housing back to the reservoir at the end of a defrosting period, and controlled by the pressure of the refrigerant from the evaporator means for automatically controlling the delivery 1 of water by the pump from the reservoir to the tank for defrosting periods and draining the water from the housing back to the reservoir at the end of said periods.

3. The combination with a housing adapted to retain a body of water, an evaporator in the 'ousing having frost accumulatin surfaces, and means for circulating refrigerant through the evaporator, of a reservoir for. a body of water, a pump for forcing water from the reservoir into the housing for submerging the evaporator during a defrosting period connected to drain water from the housing back to the reservoir at the end of a'defrosting period, and means controlled by the pressure-of refrigerant from the evaporator for automatically controlling the delivery of water by the pumpfrom the reservoir to the tank and draining the water from' the housing back to the reservoir at the end of a defrosting period. v

4. The combination with a housingadapted to retain a body of water, an evaporator in the housing having frost accumulating surfaces, and means for circulating refrigerant through the evaporator, of means for delivering water from a supply under pressure into the housing for erant from the evaporator for controlling the valve means.

5. The combination with a housing adapted to retain a body of water, an evaporator in the housing having frost accumulatin surfaces, and

means for circulating refrigerant through the evaporator, of means for delivering water from a supply under pressure into the housing for submerging the evaporator during a defrosting period, means for draining the water from the an -see housing at the end of a defrosting period, valve means for controlling the delivery of water to the housing and draining it therefrom, and means for automatically controlling the valve means to fill the housing for each defrosting period and to drain the housing at the end of each defrosting period.

, 6. The combination with a housing adapted to retain a body of water, an evaporator in the housing having frost accumulating surfaces, and means for circulating refrigerant through the evaporator, of means for delivering water from a supply under pressure into the housing for submerging the evaporator during a defrosting period, means for draining the water from the housing at the end of a defrosting period, valve means for controllin the delivery of water to the housing and draining it therefrom, and means controlled by the pressure of the refrigerant from the evaporator for automatically controlling the valve means for filling the housing for each defrosting period, and draining it at the end of said periods.

7. The combination with a housing adapted to retain a body of water, an evaporator in the housing having frost accumulating surfaces, and means for circulating refrigerant through the evaporator for cooling air, of a pump for delivering water into the housing to submerge the evaporator, and connected to the reservoir to drain the water from the housing, an electric motor for driving the pump to deliver water into the housing, a device responsive to pressure of the refrigerant from the evaporator, and switch means operable by said pressure responsive means for controlling the operation of the electric motor.

8. The combination with a housing adapted to retain a body ofwater, an evaporator in the housing having frost accumulating surfaces, and

means for circulating refrigerant through the,

evaporator for cooling air, of means for delivering water into the housing to submerge the evaporator, means for draining the water from the housing, valve-means for controlling the delivery means and the drain means, an electrically responsive device for controlling the valve-means to deliver water into the housing and drain it therefrom, a device responsive to pressure of the refrigerant from the evaporator, and switch means operable by said pressure responsive means for controlling the valve-means.

9. The combination with a housing adapted to retain a body of water and disposed in a low temperature refrigerating compartment, an evaporator in the housing having frost accumulative surfaces and means for circulating a refrigerant through the evaporator, ,of a reservoir disposed outside of the compartment, a pump for forcing water from the reservoir into the housing for submerging the evaporator during a defrosting period connected to drain the water from the housing into the reservoir when the evaporator has been defrosted, and means controlled by the pressure of refrigerant from the evaporator for controlling the operation of the pump.

10. The combination with a housing adapted to valve-means outside of the compartment for controlling the flow of water into the housing and draining the water therefrom, and electrical means outside of the compartment for controlling the valve-means.

11. The combination with a housing adapted to retain a body of water, an evaporator in the housing having frost-accumulating surfaces, a fan for circulating air through the housing in contact with the evaporator, an electric motor for operating the fan, and means for circulating refrigerant through the evaporator for cooling the air, of electrically controlled means for filling the housing with a predetermined quantity of water to submerge the evaporator for defrosting periods and discharging the water from the liousing at the end of said periods, a device responsive to pressure of, the refrigerant from the evaporator for automatically controlling the water delivery and discharge means and the operation of the fan-motor to stop during the defrosting periods and to start after the defrosting periods.

12. The combination with a housing adapted to retain a body of water, an evaporator in the housing having frost-accumulating surfaces, a fan for circulating air through the housing in contact with the evaporator, an electric motor for operating the fan, and means for circulating refrigerant through the evaporator for cooling the air, of electrically controlled means for filling the housing with a predetermined quantity of water to submerge the evaporator for defrosting periods and discharging the water from the housing at the end of said periods, a device responsive to pressure of the refrigerant from the evaporator and an electric switch operable by said device for controlling the water delivery and discharge means and the operation of the fanmotor to stop during the defrosting period and to start after the defrosting period.

RICHARD W. KRI'IZER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

